MELBOURNE, Australia (AFP) — Iga Swiatek admitted she was mentally "at the airport" before staging an astonishing comeback against Danielle Collins to stay alive in the Australian Open while Carlos Alcaraz returned to action.

The Polish world No. 1 was up a set and a break in her second-round match before faltering badly and slipping to a 4-1 deficit in the deciding set.

But just as she appeared to be heading home, she reeled off five straight games to win 6-4, 3-6, 6-4 and extend her winning run to 18 matches.

"Oh my God, I was at the airport already," joked Swiatek, who has never won the Australian Open.

"I wanted to fight until the end. I knew she played perfectly but it would be hard for anybody to keep that level, so I wanted to be ready for if the mistakes would come from the other side."

"It wasn't easy. I felt like I had the momentum going and then she started playing suddenly two times faster and I had no idea how to react to that for a couple of games. I came back, and I thought the only thing I could focus on was myself."

Four-time Grand Slam champion Swiatek, who will face unseeded Czech player Linda Noskova in the third round, reeled off 36 winners against 35 unforced errors.

Despite her dazzling comeback, she will know that she has to move up a gear and find more consistency if she is to progress further.

On a dramatic day at Melbourne Park, sixth-ranked Alexander Zverev and Casper Rudd, the 11th seed, were pushed to the brink before both came through their matches in fifth-set tie-breaks.

Facing a second consecutive second-round exit in Melbourne, Germany's Zverev came back to win 7-5, 3-6, 4-6, 7-6 (7/5), 7-6 (10/7) after a gripping contest lasting four-and-a-half hours on Margaret Court Arena.

"To be honest, he probably deserved to win the match more than me today, but that's tennis sometimes," said Zverev, who faces unseeded American teenager Alex Michelsen next, who upset Czech 32nd seed Jiri Lehecka.